The paper notes that the last two and a half years have been a whirlwind of growth for DoubleLine. The company launched its first mutual fund in April 2010. Currently, it has more than $53 billion in assets under management. In 2012 alone, DoubleLine's asset base more than doubled, according to the mutual fund research firm Strategic Insight. The paper notes that Businessweek labeled it the "fastest-growing mutual fund startup in history."

With that in mind, Gundlach says he expects to close the DoubleLine Total Return Bond to new investors in late 2013 or early 2014. Gundlach says closing the fund, which currently has $38 billion in assets, is necessary to keep it at a manageable size.